This essay has taken up much of my time, and more of my energy, for the past ten years. It has been impossible to be my friend during this period without enduring countless conversations and scribblings devoted to one or nother line of thought. As a result, my friends have contributed enormously to the final product. While I will refrain from a blow-by-blow account, this book would never have emerged without their ceaseless criticisms and encouragements.It is easier to be more specific in detailing my other debts. Judith Shklar, by her personal example, introduced me to the reality of political philosophy while I was a student of hers at Harvard College. Proceeding to the Yale Law School in the mid-1960s, I encountered a group of teachers who gave Shklar's message a new force: Alexander Bickel, Robert Bork, Guido Calabresi, Ronald Dworkin, Charles Reich. While these people were very different from one another, they convinced me that political action was futile without systematic reflection.